The compounds of formula I are valuable intermediate products in the chemical synthesis of various pharmaceutical active substances (e.g. A. Nuhrich et al., Eur. J. Med. Chem. 31, 12, 1996, 957-964), or are pharmaceutical active substances themselves, particularly NMDA receptor modulators (e.g. A. H. Lewin et al., J. Med. Chem, 1998, 41, 988-995).
By hydrogenation of tropanone-oximes in the presence of a platinum catalyst and a diluent under elevated pressure (e.g. S. Archer, J. Am. Chem. Soc. 80, 1958, 4677), N-substituted 3-aminonortropanes are predominantly obtained in the α form.
By reacting tropanone-oximes with metallic sodium in an alcohol (e.g. A. Nuhrich et al., loc. cit) predominantly the β-isomers of the N-substituted 3-aminonortropanes are obtained.
However, this process is of only limited use for large-scale industrial production for safety reasons.
The aim of the present invention was therefore to propose a method of producing N-substituted 3β-aminonortropanes of formula I which can be carried out on an industrial scale, with high yields and with favourable space/time ratios. The invention also set out to provide 3β-aminonortropanes of formula I which are substantially free from the corresponding 3α-isomers.
This objective was achieved according to the invention by the provision of a process in which the 3β-aminonortropane is obtained starting from a correspondingly substituted 3-oxonortropane or a correspondingly substituted 3α-aminonortropane.
The process according to the invention makes it possible to prepare 3β-aminonortropanes on an industrial scale in a high yield and purity.